The Solidaritätszuschlag, a surcharge on income tax, was first levied from 1 July 1991 to 30 June 1992. From 1995 it was levied again, without a time limit, to finance German unity. Since 2021 about 90 percent of those who paid it are fully exempt. In March 2025 the Federal Constitutional Court rejected a complaint against it. Such a surcharge need not be limited in time from the start, the court held. It must be abolished or adjusted only when the extra financial need behind it has evidently ended. Germans have a saying for this: Nichts hält länger als ein Provisorium, nothing lasts longer than a provisional arrangement.